This invention relates to means for accurately mounting and locking dies in operating position. While the invention will hereinafter be described for purposes of illustration as applied to a punch press, for instance a machine for pinch-pointing screws, it will be understood that application of the invention is not thus limited.
In U.S. Pat. No. 3,398,413 issued Aug. 27, 1968, in my name, there is shown and described, with particular reference to FIG. 4 thereof, a pair of complemental dies relatively movable to pinch-point metal blanks. Each die is disclosed as being located and secured in a pocket of a die holder by means of a clamping screw having a conical end received in a conical recess in the die, the axes of the screw and the recess being offset to precisely maintain the operating positions of the dies.
While the patented arrangement has been found to work well in high speed screw pre-pointing machines, the advent of drill screws and other factors, has necessitated the use of higher forming pressures on the dies thus tending to put strain on the clamping screws and to work each die with resultant fret corrosion of its die pocket. To attain rigid holding of a die by a means convenient to use is critical. Resorting to a larger size of clamping screw unfortunately does not solve the problem of providing greater die holding power since to do so within the space limits available (and allowable due to other elements of the machine) necessitates a larger hole and the consequently weakened pocket is likely to break thereat.